1. Field of the Invention
Aspects of the present invention relate to a mask device, a method of fabricating the mask device with improved reliability, a method of manufacturing a large-sized division mask device by forming a striped aperture parallel to the roll direction and a method of fabricating an organic light emitting display device (OLED) using the mask device.
2. Description of the Related Art
Recently, in order to solve problems with a conventional display device such as a cathode ray tube, people have been developing flat panel display devices such as liquid crystal display devices, organic light emitting display devices (OLEDs), plasma display panels, and so on.
In fabricating an OLED, an emission layer for emitting electrons to excite each of red (R), green (G) and blue (B) phosphors is formed using an evaporation method. The evaporation method is a method of inserting the raw material of the emission layer into a crucible in a vacuum chamber, and heating the crucible to evaporate the raw material to form a specific layer on a substrate. In this process, a mask is mounted in the vacuum chamber, and the raw material of the emission layer is evaporated in the pattern of the mask to form the emission layer having the designed patterns for R, G and B.
FIGS. 1A and 1B are plan views of a conventional mask device. Referring now to FIG. 1A, a conventional mask passes through a rolling process using a roller 1 formed of stainless steel or other metal materials to form a mask substrate 2. Then, using a photolithography method, the mask substrate 2 is etched to form an aperture region 3 and a blocking region 4, thereby completing the mask.
When the aperture region 3 and the blocking region 4 are formed after the rolling process on the mask substrate 2 using the photolithography method, the rolled direction of the mask substrate 2 is perpendicular to the stripe direction of the aperture region. However, as described above, in the case of the mask having a stripe pattern of the aperture region perpendicular to the rolled direction, it is difficult to adapt the mask to a large-sized substrate because of the limitation of the width of the mask substrate 2.
In addition, as shown in FIG. 1B, there is a variance in quality between the center area and the outer areas of the mask substrate 2, i.e., striped apertures are irregularly arranged, not aligned in a straight line. In FIG. 1A, the variance in quality is shown in the same direction as the rolled direction. In the conventional art, when the striped aperture region is formed using the photolithography method, the striped aperture region is formed close to the outer parts of the mask substrate, and is not formed in a straight direction because of the variance in quality between the center part and the outer parts of the rolled mask substrate 2. That is, because there is a small margin relative to the striped aperture region of the mask, it is difficult to obtain a reliable pattern during the subsequent patterning process using a mask. As a result, the reliability of the mask may be less than desired.